In many environments, it is desirable to use crane trolley-hoists to lift and move large loads. Crane trolley-hoists comprise a trolley mounted on a long overhead support, usually an I-beam. The trolley is moved back and forth by appropriately energizing a trolley motor. When the trolley motor is energized, wheels that ride on the support rotate to move the trolley in one direction or the other. The trolley supports a hoist that is used to raise and lower a load. While some trolley hoists are manually actuated, many are powered. If the hoist is powered, the energization of a hoist motor mounted on the trolley causes the hoist to raise or lower a load supported by the hoist. Power to trolley and hoist motors is frequently controlled via a pendant hanging from the trolley.
Crane trolley-hoists are powered either by electric or pneumatic motors. Which type of power is chosen in a specific situation depends upon a variety of factors, such as the type of power available and the nature of the environment in which the crane trolley-hoist is to be used. In certain corrosive environments, such as on board ships, at ship loading docks, or in certain types of chemical plants, pneumatic crane trolley-hoists are often more desirable than electric crane trolley-hoists because they are less likely to break down. In the past, one major objection to the use of pneumatic crane trolley-hoists in such environments has been the lack of a well-sealed pendant suitable for controlling the trolley and hoist motors. This invention is directed to overcoming this disadvantage.